A typical modular conveyor belt is disclosed in U.S. Pat. No. 3,870,141 issued to J. M. Lapeyre on Mar. 11, 1975. According to this patent, identical modules formed by injection molding are pivotally connected to one another to form a conveyor belt of a desired length and width. Each module includes a plurality of elongated elements, each of which has a first pivot end and a second pivot end. The plurality of elongated elements are connected together such that apertures defined in each of the first and second pivot ends lie along a first and second pivot axes respectively, which pivot axes are parallel one to the other. The pivot ends of one module are intermeshed and pivotally connected by means of a pivot rod to the pivot ends of another module until an entire belt having a desired length and width is formed. The plastic belt built according to the teachings of this invention has been well received by industry and has many particular uses. The module itself is typically injection molded out of plastic by means of a simple two-piece mold which includes two "halves". One "half" typically molds the bottom portion of the module and the other half typically molds the top portion. In such simple two piece molds, however it will be appreciated that it is impossible to mold complex upper conveying surfaces and at the same time eliminate all excess plastics since such molding would result in undercuts and make it impossible for the mold halves to separate.
U.S. Pat. No. 4,171,045 issued on Oct. 16, 1979 also to J. M. Lapeyre recognized the need for including a conveying surface which would not allow objects riding on the conveyor surface to slip and thereby allow the belt to pass underneath. The belt disclosed and formed by the teachings of U.S. Pat. No. 4,171,045 is similar to that of the U.S. Pat. No. 3,870,141 discussed heretofore except that selected ones of elongated members include a plurality of "dogs" which extend above the normal portion of the conveying surface to contact and push articles on the conveying surface such that the belt will not slip underneath. However, it can be seen that such a conveying surface is still rather simple and can readily be injection molded by mold halves, one-half of which molds the bottom portion of the module and the other half which molds the top half.
In a similar manner, U.S. Pat. No. 4,213,527 issued June 22, 1980 to Lapeyre, et al, further discloses a module for forming a link conveyor belt which has ridges or flight members extending transverse to the direction of travel for preventing the conveyor belt from slipping under articles riding on the conveyor surface. A study of this patent, discloses that the particular modules maybe molded by an extrusion process and then the link ends cut in by blades. Similarly, U.S. Pat. No. 4,170,281 issued on Oct. 9, 1979 and 4,080,842 issued on Mar. 28, 1978, both to Lapeyre, also show conveying belts having members extending transverse to the conveying surface for moving articles on the conveying surface along the belt such that the belt cannot slip underneath the article. Again, these patents may readily be molded by a simple two-piece mold one-half of which molds the bottom half of the module and the other half molds the top half of the module.
Still other module link conveyor belt patent applications by Lapeyre and/or owned by the same assignee as the present invention which might be considered relevant to the present invention include: Ser. No. 483,210 entitled "Link Chain Belt" filed Apr. 14, 1983 now U.S. Pat. No. 4,993,543; Ser. No. 179,523 entitled "Modular Center Drive Conveyor Belt" filed Aug. 19, 1980 now U.S. Pat. No. 4,832,187, May 23, 1989; and Ser. No. 457,482 entitled "Lightweight Modular Conveyor Belt" filed Jan. 12, 1983 now U.S. Pat. No. 4,821,872, Dec. 3, 1985. In addition, two patent applications entitled "Conveyor Belt Having Insertable And Selectable Conveying Members" now U.S. Pat. No. 4,832,183, May 23, 1989 and "Conveyor Belt Having A High Friction Conveying Surface" filed concurrent with the present application now U.S. Pat. No. 4,925,013, May 15, 1990 disclose subject matter having some similarity to the present application.
Thus, a review of the prior art patents as well as pending applications of the assignee of the present invention reveals that except for the module formed by the extrusion process described in U.S. Pat. No. 4,213,527 discussed heretofore, to date all molding of conveyor belt modules has been by the two-piece molding process wherein the one-half of the mold molds the bottom portion of the module and the other half of the mold, molds the top portion of the module. Further, by such an injection molding technique it is not possible to mold a complex upper conveying surface. Therefore, it is an object of this invention to provide a module for forming a conveyor belt which belt has a complex upper conveying surface.
It is another object of the present invention to provide a simple and inexpensive method of injection molding modules having a complex upper surface.